You can also try microwave curing for early setting and strength gain. Check the paper entitled "Use of microwave energy for accelerated curing of concrete: a review" by Makul N, Chatveera B, Ratanadecho P

Thank you Kasim, I will check it out this paper. The point is not to alter the concrete micro-structure too much.

Best regards

I think your drying process is more or less the simplest way to speed it up. You must realize, however, that the surfaces of the cylinder will become very dry and most probably crack. That is perhaps not important here.

What is more important is how you will "calibrate" the TDR from such a measurement. You will get moisture profiles in your cylinder with very dry surfaces and initially very wet conditions in the center. Whatever reading you get from the TDR will be a part of this moisture profile, mainly in the center if you place the TDR-probe there. The weight loss of the cylinder will represent the changes of the moisture profile in the whole cylinder all the way out to the surfaces. All of that will not be registered by the TDR.

I think you should consider to perform the calibration procedure in another way. It is not an easy task, but this is how I would do it, if I had to:

1. Dry the cylinder stepwise to equilibrium at a high temperature (say +50C) but in a climate box with a saturated salt solution (and a fan) to reach equilibrium with the RH that this salt solution will give. In this way you avoid to dry the surfaces too much and you avoid the effects of hysteresis at the surfaces as you would get if you just sealed the cylinder after some drying and waited for redistribution. Determine the weight before and after drying.

2. Repeat the procedure with a new salt solution that gives a lower RH.

3. ... and so on!

Reference: Tang L. & L.-O. Nilsson (1993) Effect of drying at an early age on the moisture distributions in concrete specimens used for air permeability test. Nordic Concrete Research, Publ No 13, 2/1993, pp 88-97.

Thank you Mr Nilsson. Your answer is consistent with our opinion on the "calibration". We are currently involved in numeric simulation to assess the evolution of the moisture gradient between the core and the edge of the sample. The salt solution is also a way we are exploring to control the drying of the concrete.

By the way, I didn't find your article on the NCR websit (only the abstract). I would be very interested by a full-text copy of this article.

Thanks a lot for your kind answer and your relevant and useful advice.

Best regards

As we know, TDR readout for concrete depends higly on temperature and is important even in the range 20-50 Celsius. You should make measurements always in the same temperature otherwise you will get erroneus data.

If you would like to speed up the drying process you can try lower the pressure surrounding the specimen.

We were thinking about de-pressurized the environment. We don't know of it is efficient or not, we would be glad to get feedback. We were aware of the temperature dependence, but we have to quantify it more accurately . Thank for your useful comment

Salut Alexis, I suggest you read this article : Basile T Tamtsia, James J Beaudoin, Basic creep of hardened cement paste A re-examination of the role of water, Cement and Concrete Research, Volume 30, Issue 9, September 2000, Pages 1465-1475. Some drying methods (for cement paste) are discussed, as well as their impact on the microstructure of the cement paste, including the use of vacuum and elevated temperatures.

Thanks Laurent! See you next week, face to face !